1. Field of the Invention
The present invention relates to a safety gear designed to be mounted on an elevator car, which car moves along guide rails, said safety gear having a frame provided with one or more bars or the like placed transversely relative to the frame and a safety gear housing which can be moved laterally on said bars or the like and contains at least one wedge movable relative to the safety gear housing.
2. Description of Related Art
The motion of an elevator car is guided by roller guide shoes or sliding guide shoes moving along guide rails. The elevator is provided with safety gears, mounted e.g. on the car unit, which are activated when the elevator speed increases too much. The safety gears grip the guide rails in the hoistway. A sliding safety gear is provided with sliding surfaces having a high coefficient of friction. When the safety gear is activated, the sliding surfaces are pressed against the guide rail, retarding or stopping the elevator motion by means of friction. The sliding surfaces may consist of wedges movable in wedge housings.
For the sake of travelling comfort, the guide shoes are generally provided with relatively soft springs. The clearance between the wedges and the guide rail is usually relatively small (typically 3 . . . 5 mm). Therefore, the elastic play of the guide shoes must be less than the distance between the wedges and the guide rail to prevent accidental gripping of the safety gear. When the speed increases, a larger elastic play is required. This means that the clearance between the wedges and the guide rail should also be increased, because this clearance must always be larger than the elastic play of the guide shoes. However, a larger clearance between the wedges and the guide rail involves technically difficult and complex structures. As the wedge angle must remain within certain limits, increasing the clearance means that the wedge and the safety gear must be considerably longer. In limited spaces, this is a serious drawback.